Electromagnetic relay



w. H. D. FORD.

ELECTROMAGNETIC RELAY.

APPLICATION FILED APR.13| l9l8.

1,374, 1 98. Patented Apr. 12, 1921.

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W W My UNITED STATES PATENT OFFICE. 7

mm H. D. FORD, OF YONKERS, NEW YORK, ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION 01 NEW YORK.

ELECTROMAGNETIC RELAY.

Specification of Letters Patent. Patented Apr. 12, 1921.

Application filed April 13, 1918. Serial No. 228,407.

7 clear, concise, and exact description.

This invention relates to electromagnetic relays and has for its object to providea relay which will not be affected by currents of a value appreciably lower than those required for its complete operation.

It is often required that a relay operate consistently on a current of a certain prescribed value and yet not be so sensitive as to be affected by a smaller current which the circuit conditions might allow to traverse the winding. In many cases there is a very small margin between the operating and the non-operating requirements, and accord ingly there results trouble due to the lowered contact pressures on the back contacts, thus making the relay particularly susceptlble to vibration.

With a view of correcting this trouble the present invention provides a structure so arranged as to prevent its being appreciably affected by currents less than the normal operating current, without serlously decreasing its operating efliciency. Th1s result 13 accomplished by providing the core wlth an extension so arranged that initially there will be a magnetic pull exerted uponthel armature by the pole piece extension 1n a direction opposite to that exerted by the pole piece itself. However, since the armature 1s adjusted somewhat closer to the pole piece, movement takes place in that direction upon the flow of a current of the required strength through the magnetizing winding.

In the accompanying drawing Figure 1 shows a well-known type of relay equipped with a pole piece extension in accordance with this invention; and Fig. 2 shows such extension member removed from the relay core. 1

Referring to this drawing, there is shown a relay of the same general type as disclosed in Craft Patent No. 1,156,671 of Octo- 'ber 12, 1915. This relay comprises the coil 5 forming an oblate winding upon the flat core 6' and retained in place upon the core .with a lug by means of the spool heads "7-7 of hard rubber or similar material. The rear portion of the core 6 is extended to provide means for mounting the armature which consists of a pair of longitudinal arms 8-8, and a transverse portion 9. Attached to the armature is the thin steel reed 10, having a pair of extended portions 11--11 which are riveted or otherwise secured to the arms 8-8. The reed 10 is held rigidly in place by means of the screws 12-12 which pass through the core extension and engage threaded holes in the plates 13, only one of which is shown. These screws also serve to hold in place the terminals 14-1 1 for the wlnding and the contact spr. '5 15 and 16. Insulating plates 17-17 are providedto insure the necessary electrical separation of parts. A threaded stud 18 of brass or other non-magnetic material is secured to the end of core 6 and is equipped with anadjusting nut 19 adapted to bearagainst the armature and limit the amount of its travel.

Attached to the core by means of the screws 26-20, which engage the threaded holes 21 21, is the U-shaped' member having a constricted portion 23 and a pole face portion 24. Since the armature 9 is located between the end of core 6 and the pole face portion 24, it is acted upon by forces in opposite directions upon energization of coil 5. Upon armature 9 being attracted by core 6, the insulating stud 22 of hard rubber or similar material, engages contact spring 16 and causes it to break contact with spring 15. In order that the latter spring may have the desired spring tension, it is provided 25, which bears against spool head 7 and prevents the spring from following spring 16 in its movement. At the rear of core 6 there are provided lugs 2626 bent at right angles to the core itself and in opposite directions for the purpose of providing means for mounting the relay in position.

By means of the adjusting nut 19, the relative air-gaps on eitherside of the armature are adjusted so that the position of unstable magnetic equilibrium is slightly toward the core. For comparatively low operating current values, the armature is adjusted to lie in a position nearer the core, while for higher operating current values,

it is adjusted to lie closer to the portion 24 of the core extension. In the latter case the constricted portion 23 becomes saturated and the resultant magnetic pull is in the direction of the core.

This device also has the effect of slowing down the time of operation which is of considerable importance under certain conditions. Since the movement of the armature is brou ht about'by the difference in pull exerte upon the armature by two forces acting inopposite directions, it is apparent that the resultant force necessary to cause operation of the armature does not attain a sufficient value until the current through the magnetizin windin has attained a higher value t an wou d be required otherwise.

What is claimed is:

1. An electromagnetic relay-comprising a core, a magnetizing coil about said core, an armature actuated by said coil, contact springs controlled by the movement of said armature, and an extension on said core and in magnetic contact therewith adapted upon energization of the coil to exert a magnetic pull upon said armature in a direction opposite to that exerted by the core itself.

2. An electromagnetic relay com rising a core, a magnetizing coil about sai core, an armature actuated by said coil, contactsprings controlled b the movement of said armature, and a U-s iaped extension on said core and in magnetlc contact therewith adapted upon energization of the coil to exert a magnetic pull upon said armature in a direction opposite to that exerted by the core itself.

3. An electromagnetic relay comprisinga core, a magnetizing coil about said core, an armature actuated by said coil, contact springs controlled by the movement of said armature and an extension on said core adapted upon energization of the coil 'to exert a ma etic pull upon said armature in a direction opposite to that exerted by thecore itself, said extension bein provided With a constricted portion, W ereby the magnetic pull exerted by said extension is limited.

In witness whereof, I hereunto subscribe my name this 9th da of A ril, A. D. 1918.

WILEI M D. FORD. 

